As semiconductor circuits have scaled to smaller sizes, susceptibility to single event upsets (SEUs) has become a greater concern. In one approach to the mitigation of SEUs, the layout of drain contact nodes is adjusted to provide resilience against SEUs. In the LEAP (Layout design through Error-Aware Transistor Positioning) approach, the response to a single event of each individual drain contact node in the layout of the circuit is analyzed. The drain contact nodes are placed in the layout such that the drain contact nodes act together to fully or partially cancel the effect of the single event.
The LEAP approach does not mitigate SEUs that are caused through parasitic bipolar action. Through parasitic bipolar action, a transistor formed over a well of a first type may turn on if a single event in an adjacent well of a different type induces sufficient current through a transistor in the adjacent well. One approach to protecting against parasitic bipolar action is to form guard rings between P wells and N wells. Another approach is to provide further separation of the nodes in the layout. Both approaches consume sizeable amounts of die space.